140
increase in mass by addition of small grains of sand, which enter the labyrinth and are
incorporated into the otolithic membrane,” (Lychakov et al. 2000 ).
Recently, Mills et al. ( 2011 ) reported about the nature and origin of exogenous
otoconia from inner ear of Heterodontus portusjacksoni, the fi sh species known also
as Port Jackson shark. Surprisingly, these authors identifi ed within the otoconial
mass of the specimens silicon dioxide particles of exogenous origin, which were
bound within a carbon matrix. These siliceous structures are suggested to play the
similar role to the otoconia found in other species of elasmobranchs.
The outer surface of otoconia and otoliths consists mostly of precipitated
CaCO 3 , in contrast to the inner core matrix that include glycoproteins (termed
Otoconins) and proteoglycans (Thalmann et al. 2001 ; Lundberg et al. 2006 ; Deans
et al. 2010 ). In case of calcium carbonates, their crystals exist in three major
polymorphs:
– “calcite (found in mammals and birds);
– aragonite (found in amphibians and fi sh);
– vaterite (found in primitive jawfi sh such as garfi sh)” (Deans et al. 2010 ; see also
Ross and Pote 1984 ).
It is generally believed that in otoconia and otoliths the major matrix proteins,
which bind calcium and make up the organic core, are responsible for diversity of
calcium carbonate polymorphs (Pote and Ross 1991 ; Schipiani 2003 ). Principally,
it is suggested that “the organic matrix of otoconia/otoliths serves as a framework
for the inorganic CaCO 3 crystallites to deposit and grow,” (Xu et al. 2010 ; see also
Zhao et al. 2007 ).
Here, I would like to represent a short list of corresponding main matrix proteins
(for review see also Xu et al. 2010 ):
– Otoconin 90 (Oc90/95), a highly glycosylated glycoprotein to be found in
mammals and birds (Wang et al. 1998 ; Verpy et al. 1999 );
– Otoconin 22, in amphibians (Pote et al. 1993 ; Yaoi et al. 2001 );
– Otoconin 54, in primitive jawfi sh (Pote and Ross 1991 );
– (Omp) the otolith matrix protein – in teleost fi sh (Murayama et al. 2000 , 2002 ,
2004 , 2005 );
– otolin-1, in fi sh (Murayama et al. 2002 ; Davis et al. 1995 ; Deans et al. 2010 );
– Starmaker, in fi sh (Sollner et al. 2003 );
– matrix macromolecule-64, in fi sh (Tohse et al. 2008 );
– Otoc1 (zOc90), in fi sh (Petko et al. 2008 );
– Sparc, precerebellin-like protein (Cblnl) and neuroserpin, in fi sh (Kang et al.
2008 ).
The role of these proteins is very important. For example, morpholino knockdown
of Oc90 orthologs in fi sh lead to an aberrant otolith phenotype (Petko et al.
2008 ). Similarly, targeted deletion of Oc90 in mice results in balance defi cits due to
absent or abnormal (few and large) otoconia (Zhao et al. 2008 ). Also, knockdown of
Starmaker, Sparc and Otoc1, OMP, and otolin-1, lead to various abnormalities in
zebrafi sh otolith growth (Kang et al. 2008 ; Murayama et al. 2004 , 2005 ; Sollner
3 Biocomposites and Mineralized Tissues
increase in mass by addition of small grains of sand, which enter the labyrinth and are
incorporated into the otolithic membrane,” (Lychakov et al. 2000 ).
Recently, Mills et al. ( 2011 ) reported about the nature and origin of exogenous
otoconia from inner ear of Heterodontus portusjacksoni, the fi sh species known also
as Port Jackson shark. Surprisingly, these authors identifi ed within the otoconial
mass of the specimens silicon dioxide particles of exogenous origin, which were
bound within a carbon matrix. These siliceous structures are suggested to play the
similar role to the otoconia found in other species of elasmobranchs.
The outer surface of otoconia and otoliths consists mostly of precipitated
CaCO 3 , in contrast to the inner core matrix that include glycoproteins (termed
Otoconins) and proteoglycans (Thalmann et al. 2001 ; Lundberg et al. 2006 ; Deans
et al. 2010 ). In case of calcium carbonates, their crystals exist in three major
polymorphs:
– “calcite (found in mammals and birds);
– aragonite (found in amphibians and fi sh);
– vaterite (found in primitive jawfi sh such as garfi sh)” (Deans et al. 2010 ; see also
Ross and Pote 1984 ).
It is generally believed that in otoconia and otoliths the major matrix proteins,
which bind calcium and make up the organic core, are responsible for diversity of
calcium carbonate polymorphs (Pote and Ross 1991 ; Schipiani 2003 ). Principally,
it is suggested that “the organic matrix of otoconia/otoliths serves as a framework
for the inorganic CaCO 3 crystallites to deposit and grow,” (Xu et al. 2010 ; see also
Zhao et al. 2007 ).
Here, I would like to represent a short list of corresponding main matrix proteins
(for review see also Xu et al. 2010 ):
– Otoconin 90 (Oc90/95), a highly glycosylated glycoprotein to be found in
mammals and birds (Wang et al. 1998 ; Verpy et al. 1999 );
– Otoconin 22, in amphibians (Pote et al. 1993 ; Yaoi et al. 2001 );
– Otoconin 54, in primitive jawfi sh (Pote and Ross 1991 );
– (Omp) the otolith matrix protein – in teleost fi sh (Murayama et al. 2000 , 2002 ,
2004 , 2005 );
– otolin-1, in fi sh (Murayama et al. 2002 ; Davis et al. 1995 ; Deans et al. 2010 );
– Starmaker, in fi sh (Sollner et al. 2003 );
– matrix macromolecule-64, in fi sh (Tohse et al. 2008 );
– Otoc1 (zOc90), in fi sh (Petko et al. 2008 );
– Sparc, precerebellin-like protein (Cblnl) and neuroserpin, in fi sh (Kang et al.
2008 ).
The role of these proteins is very important. For example, morpholino knockdown
of Oc90 orthologs in fi sh lead to an aberrant otolith phenotype (Petko et al.
2008 ). Similarly, targeted deletion of Oc90 in mice results in balance defi cits due to
absent or abnormal (few and large) otoconia (Zhao et al. 2008 ). Also, knockdown of
Starmaker, Sparc and Otoc1, OMP, and otolin-1, lead to various abnormalities in
zebrafi sh otolith growth (Kang et al. 2008 ; Murayama et al. 2004 , 2005 ; Sollner
3 Biocomposites and Mineralized Tissues